I use a tub grinder/mixer where it grinds the hay and keeps it in the tub to mix with other ingredients. It is slower than a bale processor or a tub grinder that piles the cut feed, but it allows mixing at the same time. The end feed is totally mixed and the cows can't sort it out.
Some say a processor that lays out a swath of forage will still allow the cows to sift through and leave the coarse pieces. A tub grinder will fully cut the stems, but you then have to load some type of feed wagon to either mix 2 types of hay together or even just to feed the cows.
With the right kind of forage, bales that break down quickly, I can do a good job in a relatively short time. With coarser grasses and hard tight bales it takes some of the ability to fill the machine up away from me.
Whatever machine/system you use, processed hay is more palatable than rolled out hay. With pricey hay saving every pound is important.
Jason Trowbridge Southern Angus Farms Alberta Canada